1. Field of the Invention
The present invention relates to a semiconductor device having a package of a tape-ball grid array structure.
2. Description of the Related Art
Associating with increasing of package density of semiconductor chips, pitches of electrodes to be formed on the semiconductor chips are progressively reduced. As a result, it becomes difficult to adapt the conventional connection technology using metallic fine wire. As a package mounting the semiconductor chip to be increased the package density, various packaging technologies employing a TAB (Tape Automatic Bonding) tape have been developed and practiced. As one example, there is a TAB in QFP (Quad Flat Package) type semiconductor device which is fabricated into the conventional mold QFP form package employing the TAB tape in place of the conventional wire bonding system using the metallic fine wire. In this kind of package, contact between the TAB tape and a mold filler resin is increased by providing a slit in a heat-resistant film formed of a material, such as polyimide or the like, as the base material of the TAB tape.
In such QFP type semiconductor device employing the TAB tape, narrowing of pitch of the electrodes on the semiconductor chip can be achieved by such technology. However, in order to establish connection between such QFP type semiconductor device and an external device, external leads formed on the periphery of the QFP type semiconductor device have to be used similarly to the prior art. There is a limitation for increasing of pins required in increasing of the package density of the semiconductor chip.
As a form of the semiconductor device which can satisfy demands for narrowing of pitches of the electrodes on the semiconductor chip and increasing of pins of the semiconductor device, there has been developed a BGA (Ball Grid Array) type semiconductor device employing the TAN tape. FIG. 4 is a section of the conventional tape-ball grid array (hereinafter referred to as "Tape-BGA") type semiconductor device and FIG. 5 is a plan view of a reinforcement panel in FIG. 4.
In the Tape-BGA type semiconductor device, electrodes of a semiconductor chip 23 sealed by a sealing resin 24 are connected to leads (not show) formed on a TAB tape 22. In conjunction therewith, on the leads, solder balls 26 for external connection, are arranged in a grid-array form. As a result, a contact area for external connection can be increased without increasing occupied area in comparison with the semiconductor device connected only in the periphery as in the conventional QFP type semiconductor device. Therefore, it is advantageous to be adapted for increasing of number of pins.
However, only by the TAB tape 22, mechanical strength of the solder ball 26 forming portion for external connection becomes too small. Therefore, in the Tape-BGA type semiconductor device, the mechanical strength is improved by fixing a metallic reinforcement plate (support ring) 21 having an opening portion 21a accommodating the semiconductor chip 23 on the TAB tape 22. By the reinforcement plate 21, the strength of the sole Tape-BGA type semiconductor device can be remarkably increased. Thus, it becomes possible to avoid deformation of the semiconductor device in the fabrication process. However, upon mounting of such Tape-BGA type semiconductor device on a substrate, the following problems can be encountered.
Namely, causes to encounter the problems in mounting the Tape-BGA type semiconductor device are difference of thermal expansion coefficient of the Tape-BGA reinforcement plate and a mounting substrate, a difference of a temperature distribution of the Tape-BGA type semiconductor device and the mounting substrate upon mounting. By these causes, problem of deformation is caused in the Tape-BGA type semiconductor device. On the other hand, stress concentration can be caused in the mating portion of the Tape-BGA type semiconductor device and the mounting substrate due to difference of contraction coefficient of the Tape-BGA type semiconductor device and the mounting substrate.
On the other hand, there has been a prior art, in which radially extending slits are provided in a semiconductor chip mounting portion (island portion) of a mold package for reducing stress caused in the semiconductor chip. While radially extending slits may somewhat contribute for absorbing stress to be exerted on the semiconductor chip, they may not be effective in absorbing or eliminating stress to be exerted on the semiconductor chip upon mounting on a substrate.